/*
Copyright (C) 2005-2011 by Sankar International

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

http://en.wikipedia.org/wiki/MIT_License
 */
package com.sankarintl.algo;

/**
 * Cheap and effective to track a stream of objects for variety: detects if another object is different than any of previous.
 * Relies on the T's {@link Object#equals(Object)} for equality. Nulls are considered equal.
 * Because of mutability, the class is not thread-safe.
 * @param <T> the type to track.
 * @author Jorge A. Uveira
 */
public class VarietyTracker<T> {
  boolean hasVariety;
  boolean isFirstSet;
  T value;

  public VarietyTracker(T value) {
    this.value = value;
    isFirstSet = true;
  }

  public VarietyTracker() {}

  /**
   * Sets the new value; only if it's for the first time; if not for the first time,
   * updates the {@link #hasVariety()} value.
   * @param newVal new value from the stream.
   */
  public void setNext(T newVal) {
    if(!isFirstSet) {
      value = newVal;
      isFirstSet = true;
    }
    else {
      hasVariety |= !(
            newVal == null && value == null ||
            value != null && value.equals(newVal)
          );
    }
  }

  /**
   * Finds out if there was any variety in upcoming values
   * @return true if any of the values passed to the {@link #setNext(Object)} method were different.
   */
  public boolean hasVariety() {
    return hasVariety;
  }

  /**
   * Returns the first value passed to {@link #setNext(Object)} or null.
   */
  public T getValue() {
    return value;
  }

  /**
   * Finds out if the method {@link #setNext(Object)} has been called at all.
   */
  public boolean getIsFirstSet() {
    return isFirstSet;
  }
}

